This invention relates to a suction nozzle of high seizure efficiency for seizing the end of yarns wound in packages such as yarn bobbins obtained from spinning or winding processes. More particularly the invention relates to an improved comb which when applied to said suction nozzle provides it with this high seizure efficiency, and a method for its production.
The present invention finds application in the textile industry and in the processing and production of textile fibres, and is described hereinafter by way of non-limiting example with reference to the winding process, however it can be advantageously applied to all processes in the textile industry in which it is necessary to seek and seize a yarn end from a cylindrical or conical yarn package.
The technical problem confronted and solved by the present invention is described hereinafter with reference to FIGS. 1A and 1B.
The yarn package 1 is wound with yarn 2 by rotating the package about the axis 3 in the direction of the heavy black arrow by means of the rotary drive roller 4 against which it rests and by which it is driven by friction at constant linear speed.
When a breakage in the yarn 2 occurs, a sensor not shown in the figure senses this interruption and causes stoppage of the winding procedure, which can be restarted when the ends of the interrupted yarn have been joined together. It is therefore necessary to seek and seize the yarn ends from the feed side and from the forming package side 1. The seizing of the yarn end on the package side 1 is generally effected by a suction nozzle 5 of elongated shape which is moved up to a generator of the package 1.
The package 1 is rotated in the opposite direction to that of normal winding, i.e. in the direction of the white arrow (FIG. 1B), by a supplementary drive not shown on the figure, and the yarn end 6 is sucked by the nozzle 5 along a length which is sufficient to reliably retain the yarn, this length being greater than that necessary for the subsequent operations for restoring continuity to the yarn 2. The nozzle is then moved so that it conveys the seized yarn end 6 to the yarn joiner which restores the continuity of the yarn 2 and allows winding to restart.
If the yarn end 6 does not encounter obstacles, as it is unwound by the effect of the contrary rotation of the package it flows into the suction nozzle 5 along the more forward lip 7 of the nozzle, and no problems are encountered, as shown in 6A in FIG. 1B and FIG. 1C.
A technical problem, to be solved by the invention, may however arise in that the yarn end 6 may not unwind easily from the package 1 either because it adheres to the hairiness of the yarn turns adjacent to it or because the winding is imperfect. In this case the yarn end 6 finds itself in the situation indicated by the dashed line 6B. The yarn end moves to the opposite lip 8 of the nozzle and the counter-rotation of the package tends to withdraw the yarn end 6 from the mouth 5, so that the yarn end cannot be correctly recovered and seized.
To obviate this drawback, which seriously hinders the restoration of yarn continuity because the mouth is unable to convey the yarn end to the joining members, it is known in the art to apply inserts to that lip 8 which is more set back from the normal level of the arriving yarn end to be seized, these inserts increasing the retention action on the yarn and being in the form of irregular-surface inserts, toothing, angular blades or toothed blades, as described in U.S. Pat. Nos. 2,857,113, 3,361,372, 4,550,886 or as has been provided in the AUTOCONER winder of W. Schlafhorst & Co. since 1970.
These inserts are generally applied in the form of an angular blade 9 fixed to the outer edge of the lip 8 such that its comb toothing 10 extends towards the interior of the aperture of the nozzle 5, they then exerting a retention action on the sucked yarn end which overcomes the resistance of the yarn end to its proper unwinding. These angular blade inserts 9 are constructed in the known art by very complicated and costly methods starting from an angular-bent blade.
In one known embodiment shown in FIG. 2, a plurality of small substantially cylindrical pins 13 are applied by brazing 12 to a blade 11 already shaped to an acute angle, so that they lie a predetermined uniform distance apart along the outer edge of the side bent at an acute angle. Holes 14 are provided in the opposite side to fix the thus toothed blade 11 to the lip 8.
In a further known embodiment shown in FIGS. 3 3A, and 3B that side of the blade 11 bent at an angle is firstly machined to remove its end part 15 shown by hatching (FIG. 3A) after which its thin edge is machined with a profiled front grinding wheel to create the toothing 16 (FIG. 3B) of skew pyramid shape.
These techniques are very complicated and costly because each blade has to be individually formed, and the resultant combs can cause problems because if the teeth are very tall they tend to tear the yarn and become clogged with individual fibres, whereas if they are very short they insufficiently grip the yarn end.